1. Field of the Invention
The invention relates to a network analyzer and a method for the operation of a network analyzer.
2. Discussion of the Background
Often, the 10-term calibration method is used for the calibration of network analyzers. The published German specification DE 199 18 697 A1 discloses a calibration method of this kind. However, it is characterized by a large number of required calibration measurements. The demands on the calibration standards used are also high. Accordingly, only transmissionless calibration standards cannot be used with the conventional 10-term calibration method. Also, only unknown calibration standards cannot be used. Moreover, long-term stable, largely ideal switches for switching between the source port and the load port are required, because the influence of the switches on the calibration cannot be eliminated. However, it is advantageous with the conventional 10-term calibration method, that a very high accuracy of calibration can be achieved with it. It is also advantageous with the conventional 10-term calibration method, that measurements can be implemented on only 3 measuring points at the same time. Accordingly, one measuring point can be omitted.
The published German patent application DE 10 2005 005 056 A1 discloses a further method for the calibration of network analyzers with the 7-term calibration method. By contrast with the 10-term calibration method, the 7-term calibration method requires a smaller number of measurements and allows greater flexibility with regard to the calibration standards used. The partial use of transmissionless calibration standards is also possible. The influence of the switches on the correction calculation continues to be eliminated. Accordingly, non-long-term stable switches can be used. Also, the switches need not provide largely-ideal switching properties. However, it is disadvantageous with the conventional 7-term calibration method that measurements must be implemented simultaneously at 4 measuring points. If a signal is supplied by means of a generator to a source port of the device under test, both the signal emitted by the generator and also the signal reflected from the device under test can be measured without difficulty. The signal passes through the device under test at least partially and is emitted at a terminated load-port end. The emitted signal optionally already provides a significantly lower power, but can still be measured without difficulty. However, the signal reflected at the terminal resistance provides an extremely small power. This leads to a high noise level at the corresponding measuring point. A dynamic loss of the measurements of, for example, 20 dB is the consequence.